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The degree sequence of a graph is the sequence of the degrees of its vertices. If $\pi$ is a degree sequence of a graph $G$, then $G$ is a realization of $\pi$ and $G$ realizes $\pi$. Determining when a sequence of positive integers is…

Combinatorics · Mathematics 2022-11-28 Jiyun Guo , Miao Fu , Yuqin Zhang , Haiyan Li

Given a collection $\mathcal{G} =\{G_1,G_2,\dots,G_m\}$ of graphs on the common vertex set $V$ of size $n$, an $m$-edge graph $H$ on the same vertex set $V$ is transversal in $\mathcal{G}$ if there exists a bijection $\varphi…

Combinatorics · Mathematics 2024-06-21 Yangyang Cheng , Wanting Sun , Guanghui Wang , Lan Wei

Let $T$ be an oriented tree on $n$ vertices with maximum degree at most $e^{o(\sqrt{\log n})}$. If $G$ is a digraph on $n$ vertices with minimum semidegree $\delta^0(G)\geq(\frac12+o(1))n$, then $G$ contains $T$ as a spanning tree, as…

Combinatorics · Mathematics 2024-07-25 Felix Joos , Jonathan Schrodt

In this paper, we introduce a new concept namely degree polynomial for vertices of a simple graph. This notion leads to a concept namely degree polynomial sequence which is stronger than the concept of degree sequence. After obtaining the…

Combinatorics · Mathematics 2020-09-02 Reza Jafarpour-Golzari

A classic theorem of Dirac from 1952 states that every graph with minimum degree at least n/2 contains a Hamiltonian cycle. In 1963, P\'osa conjectured that every graph with minimum degree at least 2n/3 contains the square of a Hamiltonian…

Combinatorics · Mathematics 2015-01-08 Louis DeBiasio , Safi Faizullah , Imdadullah Khan

For many types of graphs, criteria have been discovered that give necessary and sufficient conditions for an integer sequence to be the degree sequence of such a graph. These criteria tend to take the form of a set of inequalities, and in…

Combinatorics · Mathematics 2013-01-15 Jeffrey W. Miller

A typical Dirac-type problem in extremal graph theory is to determine the minimum degree threshold for a graph $G$ to have a spanning subgraph $H$, e.g. the Dirac theorem. A natural following up problem would be to seek an $H$-factor, which…

Combinatorics · Mathematics 2025-09-30 Allan Lo

Let $H_n$ be a $k$-graph on $n$ vertices. For $0 \le \ell <k$ and an $\ell$-subset $T$ of $V(H_n)$, define the degree $\deg(T)$ of $T$ to be the number of $(k-\ell)$-subsets~$S$ such that $S \cup T$ is an edge in~$H_n$. Let the minimum…

Combinatorics · Mathematics 2014-10-15 Allan Lo , Klas Markström

Let $G$ be an $r$-uniform hypergraph on $n$ vertices such that all but at most $\varepsilon \binom{n}{\ell}$ $\ell$-subsets of vertices have degree at least $p \binom{n-\ell}{r-\ell}$. We show that $G$ contains a large subgraph with high…

Combinatorics · Mathematics 2018-04-17 Victor Falgas-Ravry , Allan Lo

For a given graph $H$, we say that a graph $G$ has a perfect $H$-subdivision tiling if $G$ contains a collection of vertex-disjoint subdivisions of $H$ covering all vertices of $G.$ Let $\delta_{\mathrm{sub}}(n, H)$ be the smallest integer…

Combinatorics · Mathematics 2025-04-30 Hyunwoo Lee

An edge-coloured graph $G$ is called $properly$ $connected$ if every two vertices are connected by a proper path. The $proper$ $connection$ $number$ of a connected graph $G$, denoted by $pc(G)$, is the smallest number of colours that are…

Combinatorics · Mathematics 2018-06-26 Xiaxia Guan , Lina Xue , Eddie Cheng , Weihua Yang

A graph $G$ is said to have \textit{bandwidth} at most $b$, if there exists a labeling of the vertices by $1,2,..., n$, so that $|i - j| \leq b$ whenever $\{i,j\}$ is an edge of $G$. Recently, B\"{o}ttcher, Schacht, and Taraz verified a…

Combinatorics · Mathematics 2015-03-17 Hao Huang , Choongbum Lee , Benny Sudakov

We conjecture that every $n$-vertex graph of minimum degree at least $\frac k2$ and maximum degree at least $2k$ contains all trees with $k$ edges as subgraphs. We prove an approximate version of this conjecture for trees of bounded degree…

Combinatorics · Mathematics 2018-08-29 Guido Besomi , Matías Pavez-Signé , Maya Stein

The celebrated Hajnal-Szemer\'edi theorem gives the precise minimum degree threshold that forces a graph to contain a perfect K_k-packing. Fischer's conjecture states that the analogous result holds for all multipartite graphs except for…

Combinatorics · Mathematics 2015-09-15 Peter Keevash , Richard Mycroft

In 1975 Bollob\'{a}s, Erd\H{o}s, and Szemer\'{e}di asked what minimum degree guarantees an octahedral subgraph $K_3(2)$ in any tripartite graph $G$ with $n$ vertices in each vertex class. We show that $\delta(G)\geq n+2n^{\frac{5}{6}}$…

Combinatorics · Mathematics 2025-06-24 Yihan Chen , Jialin He , Allan Lo , Cong Luo , Jie Ma , Yi Zhao

As an extension of the Brooks theorem, Catlin in 1979 showed that if $H$ is neither an odd cycle nor a complete graph with maximum degree $\Delta(H)$, then $H$ has a vertex $\Delta(H)$-coloring such that one of the color classes is a…

Combinatorics · Mathematics 2020-02-13 Yaser Rowshan , Ali Taherkhani

For any integer $k\geq1,$ a graph $G$ has a $k$-factor if it contains a $k$-regular spanning subgraph. In this paper we prove a sufficient condition in terms of the number of $r$-cliques to guarantee the existence of a $k$-factor in a graph…

Combinatorics · Mathematics 2023-08-29 Guoyan Ao , Ruifang Liu , Jinjiang Yuan , C. T. Ng , T. C. E. Cheng

Given two $k$-graphs ($k$-uniform hypergraphs) $F$ and $H$, a perfect $F$-tiling (or an $F$-factor) in $H$ is a set of vertex disjoint copies of $F$ that together cover the vertex set of $H$. For all complete $k$-partite $k$-graphs $K$,…

Combinatorics · Mathematics 2019-03-14 Wei Gao , Jie Han , Yi Zhao

A graph $G$ realizes the degree sequence $S$ if the degrees of its vertices is $S$. Hakimi gave a necessary and sufficient condition to guarantee that there exists a connected multigraph realizing $S$. Taylor later proved that any connected…

Discrete Mathematics · Computer Science 2018-09-17 Nicolas Bousquet , Arnaud Mary

In extremal graph theory, the problem of finding the elements of a given class of graphs which contain the most cliques traces its routes back to Tur\'an's famous theorem. We consider the implications of the connectivity property of…

Combinatorics · Mathematics 2018-10-11 Corbin Groothuis